CCM signaling complex (CSC) couples both classic and non-classic Progesterone receptor signaling

Abstract

Background Breast cancer, the most diagnosed cancer, remains the second leading cause of cancer death in the United States, and excessive Progesterone (PRG) or Mifepristone (MIF) exposure may be at an increased risk for developing breast cancer. PRG exerts its cellular responses through signaling cascades involving classic, non-classic, or combined responses by binding to either classic nuclear PRG receptors (nPRs) or non-classic membrane PRG receptors (mPRs). Currently, the intricate balance and switch mechanisms between these two signaling cascades remain elusive. Three genes, CCM1-3, form the CCM signaling complex (CSC) which mediates multiple signaling cascades. Methods Utilizing molecular, cellular, Omics, and systems biology approaches, we analyzed the relationship among the CSC, PRG, and nPRs/mPRs during breast cancer tumorigenesis. Results We discovered that the CSC plays an essential role in coupling both classic and non-classic PRG signaling pathways by mediating crosstalk between them, forming the CmPn (CSC-mPRs-PRG-nPRs) signaling network. We found that mPR-specific PRG actions (PRG + MIF) play an essential role in this CmPn network during breast cancer tumorigenesis. Additionally, we have identified 4 categories of candidate biomarkers (9 intrinsic, 2 PRG-inducible, 1 PRG-repressive, 1 mPR-specific PRG-repressive, and 2 mPR-responsive) for Luminal-A breast cancers during tumorigenesis and have confirmed the prognostic application of RPL13 and RPL38 as intrinsic biomarkers using a dual validation method. Conclusions We have discovered that the CSC plays an essential role in the CmPn signaling network for Luminal-A breast cancers with identification of two intrinsic biomarkers.

mPR-Specific Actions Influence Maintenance of the Blood–Brain Barrier (BBB)

“…Likewise, silencing all three CCM (1, 2, and 3) genes led to significantly decreased protein expression of PAQR7 (mPRα) in both nPR(−) HBMVECs and HDMVECs ( Figure 1 C). Finally, decreased expression levels of CCM1 and CCM3 proteins were observed under mPR-specific PRG actions among nPR(−) HBMVECs, HDMVECs, and RBMVECs as well as nPR(+) HUVECs, reinforcing that PRG works with its agonist, MIF, synergistically to inhibit the protein expression of CCM1/3 ( Figure 1 D), as seen previously in nPR(+/−) breast cancer cells [ 5 , 7 , 8 , 16 ]. However, mPR-specific inhibition of protein expression of CCM1/3 in nPR (+/−) ECs ( Figure 1 D) is more dramatic than what was observed in either nPR(+/−) breast cancer cells [ 5 , 7 , 8 , 16 ], suggesting that mPR-specific PRG actions have a stronger effect on the stability of the CSC in microvascular ECs.…”

“…Finally, decreased expression levels of CCM1 and CCM3 proteins were observed under mPR-specific PRG actions among nPR(−) HBMVECs, HDMVECs, and RBMVECs as well as nPR(+) HUVECs, reinforcing that PRG works with its agonist, MIF, synergistically to inhibit the protein expression of CCM1/3 ( Figure 1 D), as seen previously in nPR(+/−) breast cancer cells [ 5 , 7 , 8 , 16 ]. However, mPR-specific inhibition of protein expression of CCM1/3 in nPR (+/−) ECs ( Figure 1 D) is more dramatic than what was observed in either nPR(+/−) breast cancer cells [ 5 , 7 , 8 , 16 ], suggesting that mPR-specific PRG actions have a stronger effect on the stability of the CSC in microvascular ECs. Finally, similar to our observations in nPR(+/−) breast cancer cells [ 5 , 7 , 8 , 16 ], mPR-specific PRG actions can affect the CSC stability on both transcriptional and translational levels, demonstrating multiple layers of this intricate feedback regulation, where CCM2 plays a key role as the cornerstone for the CSC ( Figure 1 ).…”

“…Similarly, our recent works also demonstrated that CCM2 is the cornerstone for the stability and functionality of the CSC in both breast cancer cells and zebrafish Ccm1/2 mutant strains [ 16 ]. These results suggest the existence of a feedback regulatory loop influencing the expression of CCM2 , based on cellular levels of CCM1 and CCM3 at the translational level [ 5 , 7 , 8 , 16 ], which was further supported by data from 293T cells (data not shown).…”

“…Similarly, our recent works also demonstrated that CCM2 is the cornerstone for the stability and functionality of the CSC in both breast cancer cells and zebrafish Ccm1/2 mutant strains [ 16 ]. These results suggest the existence of a feedback regulatory loop influencing the expression of CCM2 , based on cellular levels of CCM1 and CCM3 at the translational level [ 5 , 7 , 8 , 16 ], which was further supported by data from 293T cells (data not shown). In this report, we examined human brain microvascular endothelial cells (HBMVECs) with identical results ( Figure 1 (A-1,A-2)), further validating our previous notion that CCM2 is the cornerstone for CSC stability across multiple in vitro and in vivo models.…”

“…Our recently defined CmPn/CmP signaling networks not only emphasize the balanced modulation of the CSC (CCM signaling complex) stability through either the positive effects of classic nuclear progesterone (PRG) receptors (nPRs) or negative effects of nonclassic membrane PRG receptors (mPRs/PAQRs), but also demonstrate the existence of feedback regulations in this relationship. The unique role of the CSC was further demonstrated in the crosstalk between nPRs/mPRs-specific signaling in breast cancer cells [ 7 , 8 , 16 ]. This intricate feedback regulatory cascade is within either the CmPn or CmP signaling network, under mPR-specific PRG actions (PRG-mediated signaling only through mPRs) in nPR(+) or nPR(−) breast cancer cells, respectively.…”